Here's a good site for determining the various versions of the Tokina 28-70mm lenses.
http://www.johncaz.net/blog/tokina-at-x-pro-af-28-70mm-26-28
I have the "(PRO II WITH BAYONET HOOD)" version, and at least my copy is quite soft in the corners at 28mm. Since I typically use a 24-120mm for "freestyle" shoots, and rarely use a mid-range zoom for more planned shoots, it's one of my least used lenses.
I have the #2 as per that listing and from f/4 its acceptable in the corners (f/5.6 for Very Good i suppose), at f/2.8 i usually dont care to much what is in the corners as its out of focus most of the time.
That said for 200 Euros its a steal, i liked it more then my real Angenieux 35-70 f/2.5-3.3. I should dig the poor Tokina up sometime, i haven't used it in years

The original Nikon 24-120 f/3.5-5.6 is a lens you'd have to pay me to use to make up for the film, i suppose its versatile but prints larger then 10x15's are far to soft.